Method of producing phosphorus pentasulfide



May Il.,` 1965 J. A. rAYLon METHOD OF PRODUCING PB OSPHORUS PENTASULFIDE Filed Nov. 13. 1961 United States Patent Office Patented 'May l1, 1965 I 3,183,062 f METHOD F PRODUCING PHOSPHORUS PENTASULFIDE James A. Taylor, Rahway, NJ., assignor, by mesne assignments, to American .Agricultural Chemical Company, a corporation of Delaware a Filed Nov. 13, 1961, Ser. No. 151,667

' 5 Claims. (Cl. 23-206) This invention relates to phosphorous sulfides. More particularly, this invention relates to the manufacture of phosphorous sulfides, such as phosphorous pentasulfide, phosphorous sesquisulfide and phosphorous heptasulfide by reaction between elemental phosphorous and elemental sulfur.

Phosphorous sulfides, particularly phosphorus pentasulfide, are particularly useful in the manufacture of l chemical compounds, such as chemical compounds employed as additives vfor improving lubricating oils. l Heretofore it has been the practice to produce phosphorus sulfide, such as` phosphorus pentasulfide, by reaction between elemental phosphorus and elemental sulfur. Phosphorous sulfide is produced in the liquid phase v by reacting liquid sulfur with liquid phosphorus in a t mass of liquid phosphorus sulfide. VBy way of example,

s the reaction temperature and the heat of reaction vof the phosphorus and sulfur serves to effect distillation of the phosphorus pentasulfide which is subsequently condensed, solidified and after suitable heat treatment recovered as product. s

In the manufacture of phosphorus sulfides, particularly phosphorus pentasulfide, by reaction between elemental phosphorus and elemental sulfur, impurities in the phoslphorus and sulfur tend to accumulate in the reaction mixture comprising the molten phosphorus sulfide, with the result that from time to time the reactor containing the molten phosphorus sulfide must be purged of its contents, particularly the impurities therein. This rsometimes necessitates shutting down the manufacturing plant activity phosphorus pentasulfide.

Yet another object of this invention is to provide a process for Athe manufacture of phosphorus pentasulfide wherein extraneous impurities introduced'into the manufacturing process by the reactants, phosphorus and sulfur, are readily separated from the reaction product, phosphorus pentasulfide.

Yet another object of this invention is to provide a continuous process for the manufacture of controlled reactivity phosphorus pentasulfide employing `only ele; mental phosphorus and elemental sulfurV as the sole"re" actants.

y How these and other objects of this invention are l achieved will become apparent in the light of the accom-y panyingdisclosure made with reference to the accom.

panying drawing which schematically illustrates a process flow in accordance with ythis invention as applied to the s manufacture of phosphorus pentasulfide.

In accordance with this .invention a process for the manufacture of phosphorus sulfide, such as phosphorus sesquisulfide, phosphorus heptasulfide, particularly phosphorus pentasulfide, and mixtures thereof, wherein elemental phosphorus and elemental sulfur are reacted to form the desired phosphorus sulfide, e.g. phosphorus pentasulfide, and the resulting formed molten phosphorus sulfide vaporized and eventually recovered as product, is improved by effecting the vaporization of the phosphorus sulfide by heating the reaction mixture containing' the molten phosphorus sulfide to an elevated temperature T1 under an elevated pressure P1, the pressure P1 being suflicient to maintain the heated phosphorus sulfide at the temperature T1 in the liquid phase and thereupon introducing the resulting heated phosphorus sulfide at the temperature T1 into a flashing or vaporization zone maintained at a relatively reduced pressure P2, such as atmospheric pressure, such that the high temperature liquid phosphorus sulfide introduced thereinto is substantially completely vaporized within said flashing zone at said pressure P2 and at a relatively reduced temvaporization or flashing, such as by being passed throughY an orifice into a zone of relatively reduced pressure, sufficient heat is available in the liquid phosphorus sulfide per se, without requiring the addition of extraneous heat, to eflect substantially complete vaporization of-the phos phorus sulfide. Flash vaporization of the superheated liquid phosphorus sulfide effects a relatively simple and quick separation of the impurities therein, such as extraneous impurities and materials introduced into the phosphorus sulfide reaction mixture by the elemental phosphorus and sulfur reactants.

The high temperature, relatively high pressure heating zone wherein the molten phosphorus sulfide is heated and maintained in the liquid phase, superheated with respect to any liquid phosphorus which may be pre'sent in the relatively reduced pressure flashing or vaporization zone, is at an elevated temperature above about 900 F., such as a temperature above about 1000 F., e.g. a temperature in the range 1050'-ll50 F. in the instance of phosphorus pentasulfide. The pressure within the heating zone should be at least sufficient to maintain the heated phosphorus sulfide therein in the liquid phase.

Usually a pressure substantially above atmospheric pressure, i.e. a` pressure in the range l0-150l pounds per square inch above atmospheric pressure, or more, preferably at least about 25 pounds per square inch above.-

atmospheric pressure, is required.

The temperature' within the vaporization or flashing zone is substantially less, i.e. at least 10 degrees Fahren- ,t heit below the temperature ofthe phosphorus sulfide within the high pressure, high temperature heating zone.

is about 950-1000" F. or in the range 50-250 degrees Fahrenheit below the temperature of the liquid phosphorus sulfide within the high temperature, high pressure heating zone. Desirably, the pressure within the flashing or vaporization zone is about atmospheric pressure or slightly above atmospheric pressure and preferably at least about pounds per square inch less than the pressure within the high temperature, high pressure heating zone. The aforesaid temperatures and pressures are for the most part applicable to the manufacture of phosphorus pentasulde to which the practice of this invention is particularly applicable. Higher and/or lower temperatures and pressures may be employed in the practice of this invention when directed to the manufacture of other phosphorus sullides or mixtures thereof, such as phosphorus sequisulfide and phosphorus heptasulfide, other than substantially pure phosphorous pentasulfide.

Referring now to the drawing which discloses an embodiment of the practice of this invention as applied to the manufacture of phosphorus pentasulde of controlled reactivity, liquid sulfur at a temperature of about 300 F. is supplied from tank 10 via line 11 and liquid phosphorus at a temperature of about 190 F. is supplied from tank 12 via line 14 into reactor 15. Desirably, reactor 15 has maintained therein a mass of molten phosphorus pentasulde at a suitable elevated temperature, such as a temperature in the range 60G-800 F., more or less, the mass of molten phosphorus pentasulde within reactor 15 serving to absorb the heat of reaction between the phosphorus and sulfur to form phosphorus pentasulde, thereby aiding in controlling the reaction temperature.

Liquid sulfur and liquid phosphorus are supplied to reactor 15 substantially continuously, or intermittently if desired, in the proportions present in the desired phosphorus sulfide product, phosphorus pentasulde.

Molten phosphorus pentasulde reaction product is supplied from reactor 1S via line 16 to hold-up tank 17 which is desirably maintained at an elevated temperature in the range 60G-800 F. Hold-up tank 17 acts as a source of supply for the molten phosphorus pentasulde to the high pressure heating operation in the practice of this invention.

Molten phophorus pentasulde is supplied from hold-up tank 17 via line 18 to high temperature, high pressure heating zone 19 which, preferably, is a tube still. The molten phosphorus pentasulde travels through coil or tube 20 within heating zone or tube still 19 and therein is subjected to high temperature indirect heat exchange with hot combustion gases resulting from he combustion of fuel and air supplied to tube still 19 via conduit 21. The hot combustion gases or flue gases are removed from tube still 19 via outlet 22.

The molten phosphorus pentasulde on passing through coil or tubing 20 within tube still 19 is rapidly increased in temperature to about 1100 F. and at the same time a relatively high pressure is maintained within coil or tubing 20 within tube still 19 to prevent vaporization of the phosphorus pentasulde. A pressure of about 50 pounds per square inch gauge within coil 20 is sufficient to prevent vaporization of the phosphorus pentasulde therein. The resulting heated, high temperature, high pressure molten phosphorus pentasulde issues from tube still 19 via line 24 and is passed through expansion valve or orifice 24a directly into relatively low pressure flasher residue receiver which is maintained at a relatively low pressure, e.g. about atmospheric pressure or 0 p.s.i.g., with respect to the pressure maintained within coil 20 of tube still 19. Upon introduction into flasher residue receiver 25 the high temperature, molten phosphorus pentasulde flashes and is substantially completely vaporized therein. Extraneous solids or impurities accumulating within flasher residue receiver 25 are removed from time to time via conduit 26. l

Vaparous phosphorus pentasulde leaves flasher residue receiver 25 via conduit 28 and enters reflux column 29, which may be a packed column wherein a small amount of condensation of phosphorus pentasulde may take place with resultant scrubbing of the phosphorus pentasulfide vapors passing upwardly through column 29. Vaporous phosphorus pentasulde leaves the top of reflux colum 29 via conduit 30 at an elevated temperature, such as about 970 F., substantially the same temperature as that maintained within flasher residue receiver 25.

The vaporized phosphorus pentasulde is then supplied via conduit 30 through condenser 31 wherein the phosphorus pentasulde is condensed. The resulting condensed, liquid phosphorus pentasulde is supplied from condenser 3l via conduit 32 through heat exchanger 34 where it is cooled to about 60G-700 F., more or less. The resulting cooled, liquid phosphorus pentasulde leaves heat exchanger 34 via conduit 35 and is supplied to combination ilaker-devitrifier 36.

lThe interior of aker-devitrier 36 is maintained in an y inert atmosphere, such as substantially oxygen-free flue gases, nitrogen, carbon dioxide and the like. The molten phosphorus pentasulde is introduced via conduit 35 into fiaker-devitrifier 36 and pan 38 therein. drum 39 is disposed within flaker-devitrifier 36 to rotate therein such that the chilled outside surface of aker drum 39 dips into the mass of molten phosphorus pentasulfide within pan 38. Upon rotation of aker drum 39 in contact with phosphorus pentasulde in pan 38 the phosphorus pentasulde is chilled and solidified on the surface of flaker drum 39 and upon continued rotation of aker drum 39 the resulting chilled, solidified, phosphorus pentasulde thereon comes into contact with scraper 40 and is removed and transferred thereon to devitrification section of flaker-devitrifier 36. The aked phosphorus pentasulde solids are moved along within the divtrification section of flaker-devitrifier by screw conveyor 41 operated by motor 42 while at the same time being subjectcd to suitable heat treatment therein to adjust the reactivity of the aked solid phosphorus pentasulde to the desired reactivity. Depending upon the time of heat treatment of the tlaked, solid phosphorus pentasulde within the devitrifier section and/or the temperature of heat treatment therein, the reactivity ofthe phosphorus pentasulde is controlled and adjusted.

Reference is made to copending, coassigned U.S. patent application Serial No. 39,391, filed June 28, 1960, in the name of Robert F. Roth and James A. Taylor, now abandoned which discloses the heat treatment operation for adjusting the reactivity of phosphorus suldes, such asphosphorus pentasulde. The disclosures of the aboveidentified U.S. patent application are herein incorporated and made part of this disclosure.

In the operation of the devitrificationsection of flakerdevitrier 36 the Baked phosphorus pentasulde solids are subjected to an elevated temperature, such as in the range about 390 F. up to the melting point of the phosphorus pentasulde, for a sufficient period of time to adjust the reactivity of the phosphorus pentasulde to the desired;`

Water cooled screw 50 cools the devitrified phosphorus pentasulde and moves it to outlet line 52 wherein it is discharged from cooler 49 for further processing such as grinding and packing.

Although particular emphasis has been placed in the disclosure of this invention, as illustrated in the accompanying drawing, on the manufacture of phosphorus pentasulfide, the benefits and advantages of this invention are Chilled aker also applicable to the manufacture of other phosphorus I suldes and mixtures thereof.

As vwill be apparent to those skilled in the art in the light of the foregoing disclosure, many modifications, alterations and substitutions are possible in the practice of this invention without departing from the spirit or scope thereof.

What is claimed is: Y

1. A method of vaporizing phosphorus pentasullide vto separate said phosphorus pentasulfde from extraneous materials contained as impurities therein which comprises heating a mass of molten phosphorus pentasullide to an elevated temperature under conditions such that substan- V tially all of the resulting heated phosphorus pentasulde phosphorus pentasulfide is maintained prior to introducing it'into said ashing zone.

3. A method in accordance with claim` l wherein the temperature of the molten phosphorus pentasulfde is about 1100 F. prior to introduction into said flashing zone. v I

4. A method of producing phosphorus pentasulfde which comprises introducing separate streams of sulfur and phosphorus into a reaction zone to effect reaction between phosphorus and sulfur therein to yield a molten mass of phosphorus pentasulde having extraneous materials cou-` taine'd as impurities therein, introducing the resulting molten phosphorus pentasulde into a heating zone maintainedat an elevated pressure to retain substantially all of the molten phosphorus pentasulde introduced thereinto in the liquid phase and heating the phosphorus pentasuliide introduced thereinto to an elevated temperature above about 1000 F. and thereupon introducing the redashing zone maintained at substantially atmospheric pressure under conditions in the absence of the addition ofextraneous heat to effect vaporization of substantially all of the phosphorus pentasullide preferentially of said con- 't .l tained impurities in said resulting molten phosphorus 1 ,v pentasulfide introduced 'thereinto and recovering the re-`v sulting vaporized phosphorus pentasulde from said liashl ing zone free of said contained impurities.

5. A method for the manufacture of a phosphorus sul iide which comprises reacting phosphorus and sulfur to' form a mass of molten phosphorus sulfide having extraneous materials contained as impurities therein, heating the resulting formed molten phosphorus sulfide at an elevated .f pressure to an elevated temperature such that when the .A

resulting heated phosphorussulde is introduced into a ashing zone maintained at about atmospheric pressure V and in the absence of the addition of extraneous heat, the

resulting molten superheated phosphorus sulfide intro- I".

duced .thereinto isk substantially completely vaporized preferentially of said contained impurities for effecting separation of said phosphorus pentasuliide from said contained impurities, condensing the resulting vaporized phosphorus sulfide, solidifyng the resulting condensed phosphorus sulde, subjecting the resulting solidied phosphorus sullide to an elevated temperature below its meltf ing point to adjust 'the reactivity thereof to a desired re#V t activity and recovering the resulting heat treated phos-` phorus sulfide having a controlled reactivity as product. v

OTHER REFERENCES Perry: "Chemical Engineers Handbook, page 585,

McGraw-Hill, New York, 1950, 3rd Edition.

sulting heated molten phosphorous pentasulide into a` MAURICE A. BRINDISI, Primary Examiner.

Brown zoz-ss. 

4. A METHOD OF PRODUCING PHOSPHORUS PENTASULFIDE WHICH COMPRISES INTRODUCING SEPARATE STREAMS OF SULFUR AND PHOSOPHORUS INTO A REACTION ZONE TO EFFECT REACTION BETWEEN PHOSPHORUS AND SULFUR THEREIN TO YIELD A MOLTEN MASS OF PHOSPHORUS PENTASULFIDE HAVING EXTRANEOUS MATERIALS FONTAINED AS IMPURITIES THEREIN, INTRODUCING THE RESULTING MOLTEN PHOSPHORUS PENTASULFIDE INTO A HEATING ZONE MAINTAINED AT AN ELEVATED PRESSURE TO RETAIN SUBSTANTIALLY ALL OF THE MOLTEN PHOSPHORUS PENTASULFIDE INTRODUCED THEREINTO IN THE LIQUID PHASE AND HEATING THE PHOSPHORUS PENTASULFIDE INTRODUCED THEREINTO TO AN ELEVATED TEMPERATURE ABOVE ABOUT 1000*F. AND THEREUPON INTRODUCING THE RESULTING HEATED MOLTEN PHOSPHOROUS PENTASULFIDE INTO A FLAHSING ZONE MAINTAINED AT SUBSTANTIALLY ATMOSPHERIC PRESSURE UNDER CONDITIONS IN THE ABSENCE OF THE ADDITION OF EXTRANEOUS HEAT TO EFFECT VAPORIZATION OF SUBSTANTIALLY ALL OF THE PHOSPHORUS PENTASULFIDE PREFERENTIALLY OF SAID CONTAINED IMPURITIES IN SAID RESULTING MOLTEN PHOSPHORUS PENTASULFIDE INTRODUCED THEREINTO AND RECOVERING THE RESULTING VAPORIZED PHOSPHORUS PENTASULFIDE FROM SAID FLASHING ZONE FREE OF SAID CONTAINED IMPURITIES. 